The effect of porous structures on the electrocatalytic activity of N-doped carbon is studied by using electrochemical analysis techniques and the result is applied to synthesize highly active and ...stable Fe–N–C catalyst for oxygen reduction reaction (ORR). We developed synthetic procedures to prepare three types of N-doped carbon model catalysts that are designed for systematic comparison of the porous structures. The difference in their catalytic activity is investigated in relation to the surface area and the electrochemical parameters. We found that macro- and mesoporous structures contribute to different stages of the reaction kinetics. The catalytic activity is further enhanced by loading the optimized amount of Fe to prepare Fe–N–C catalyst. In both N-doped carbon and Fe–N–C catalysts, the hierarchical porous structure improved electrocatalytic performance in acidic and alkaline media. The optimized catalyst exhibits one of the best ORR performance in alkaline medium with excellent long-term stability in anion exchange membrane fuel cell and accelerated durability test. Our study establishes a basis for rationale design of the porous carbon structure for electrocatalytic applications.
Lithium–sulfur (Li–S) batteries by far offer higher theoretical energy density than that of the commercial lithium-ion battery counterparts, but suffer predominantly from an irreversible shuttling ...process involving lithium polysulfides. Here, we report a fluorinated covalent organic polymer (F-COP) as a template for high performance sulfur cathodes in Li–S batteries. The fluorination allowed facile covalent attachment of sulfur to a porous polymer framework via nucleophilic aromatic substitution reaction (SNAr), leading to high sulfur content, e.g., over 70 wt %. The F-COP framework was microporous with 72% of pores within three well-defined pore sizes, viz. 0.58, 1.19, and 1.68 nm, which effectively suppressed polysulfide dissolution via steric and electrostatic hindrance. As a result of the structural features of the F-COP, the resulting sulfur electrode exhibited high electrochemical performance of 1287.7 mAh g–1 at 0.05C, 96.4% initial Columbic efficiency, 70.3% capacity retention after 1000 cycles at 0.5C, and robust operation for a sulfur loading of up to 4.1 mgsulfur cm–2. Our findings suggest the F-COP family with the adaptability of SNAr chemistry and well-defined microporous structures as useful frameworks for highly sustainable sulfur electrodes in Li–S batteries.
Compared to nanostructured platinum (Pt) catalysts, ordered Pt-based intermetallic nanoparticles supported on a carbon substrate exhibit much enhanced catalytic performance, especially in fuel cell ...electrocatalysis. However, direct synthesis of homogeneous intermetallic alloy nanocatalysts on carbonaceous supports with high loading is still challenging. Herein, we report a novel synthetic strategy to directly produce highly dispersed MPt alloy nanoparticles (M = Fe, Co, or Ni) on various carbon supports with high catalyst loading. Importantly, a unique bimetallic compound, composed of M(bpy)32+ cation (bpy = 2,2′-bipyridine) and PtCl62– anion, evenly decomposes on carbon surface and forms uniformly sized intermetallic nanoparticles with a nitrogen-doped carbon protection layer. The excellent oxygen reduction reaction (ORR) activity and stability of the representative reduced graphene oxide (rGO)-supported L10-FePt catalyst (37 wt %-FePt/rGO), exhibiting 18.8 times higher specific activity than commercial Pt/C catalyst without degradation over 20 000 cycles, well demonstrate the effectiveness of our synthetic approach toward uniformly alloyed nanoparticles with high homogeneity.
Pd is one of the most effective catalysts for the electrochemical reduction of CO2 to formate, a valuable liquid product, at low overpotential. However, the intrinsically high CO affinity of Pd makes ...the surface vulnerable to CO poisoning, resulting in rapid catalyst deactivation during CO2 electroreduction. Herein, we utilize the interaction between metals and metal–organic frameworks to synthesize atomically dispersed Au on tensile-strained Pd nanoparticles showing significantly improved formate production activity, selectivity, and stability with high CO tolerance. We found that the tensile strain stabilizes all reaction intermediates on the Pd surface, whereas the atomically dispersed Au selectively destabilizes CO* without affecting other adsorbates. As a result, the conventional COOH* versus CO* scaling relation is broken, and our catalyst exhibits 26- and 31-fold enhancement in partial current density and mass activity toward electrocatalytic formate production with over 99% faradaic efficiency, compared to Pd/C at −0.25 V versus RHE.
A gold-catalyzed tandem spiroketalization of epoxyalkynes accompanied by epoxide rearrangement into the corresponding allylic alcohol was developed for the construction of functionalized spiroketals. ...This new synthetic methodology for unsaturated spiroketals warranted a facile total synthesis of alotaketal A from carvone via a corresponding epoxyalkyne precursor.
As depressive symptom is considered a prodrome, a risk factor for progression from mild cognitive impairment (MCI) to dementia, improving depressive symptoms should be considered a clinical priority ...in patients with MCI undergoing transcranial direct current stimulation (tDCS) intervention. We aimed to comprehensively evaluate the efficacy of the home-based and remotely monitored tDCS in patients with both MCI and depression, by integrating cognitive, psychological, and electrophysiological indicators. In a 6-week, randomized, double blind, and sham-controlled study, 37 community-dwelling patients were randomly assigned to either an active or a sham stimulation group, and received 30 home-based sessions of 2 mA tDCS for 30 min with the anode located over the left and cathode over the right dorsolateral prefrontal cortex. We measured depressive symptoms, neurocognitive function, and resting-state electroencephalography. In terms of effects of both depressive symptoms and cognitive functions, active tDCS was not significantly different from sham tDCS. However, compared to sham stimulation, active tDCS decreased and increased the activation of delta and beta frequencies, respectively. Moreover, the increase in beta activity was correlated with the cognitive enhancement only in the active group. It was not possible to reach a definitive conclusion regarding the efficacy of tDCS on depression and cognition in patients with both MCI and depression. Nevertheless, the relationship between the changes of electrophysiology and cognitive performance suggests potential neuroplasticity enhancement implicated in cognitive processes by tDCS.
Reactive capture of CO2 via amino acid Xiao, Yurou Celine; Sun, Siyu Sonia; Zhao, Yong ...
Nature communications,
09/2024, Letnik:
15, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Reactive capture of carbon dioxide (CO2) offers an electrified pathway to produce renewable carbon monoxide (CO), which can then be upgraded into long-chain hydrocarbons and fuels. Previous reactive ...capture systems relied on hydroxide- or amine-based capture solutions. However, selectivity for CO remains low (<50%) for hydroxide-based systems and conventional amines are prone to oxygen (O2) degradation. Here, we develop a reactive capture strategy using potassium glycinate (K-GLY), an amino acid salt (AAS) capture solution applicable to O2-rich CO2-lean conditions. By employing a single-atom catalyst, engineering the capture solution, and elevating the operating temperature and pressure, we increase the availability of dissolved in-situ CO2 and achieve CO production with 64% Faradaic efficiency (FE) at 50 mA cm−2. We report a measured CO energy efficiency (EE) of 31% and an energy intensity of 40 GJ tCO−1, exceeding the best hydroxide- and amine-based reactive capture reports. The feasibility of the full reactive capture process is demonstrated with both simulated flue gas and direct air input.The electrosynthesis of CO via integrated capture and conversion of dilute CO2 suffers from low energy efficiency. Here, the authors report an amino acid salt-based system that employs a single-atom catalyst and operates at an elevated temperature and pressure, which enables efficient CO production.
: Insomnia is associated with elevated high-frequency electroencephalogram power in the waking state. Although affective symptoms (e.g., depression and anxiety) are commonly comorbid with insomnia, ...few reports distinguished objective sleep disturbance from affective symptoms. In this study, we investigated whether daytime electroencephalographic activity explains insomnia, even after controlling for the effects of affective symptoms.
: A total of 107 participants were divided into the insomnia disorder (n = 58) and healthy control (n = 49) groups using the Mini-International Neuropsychiatric Interview and diagnostic criteria for insomnia disorder. The participants underwent daytime resting-state electroencephalography sessions (64 channels, eye-closed).
: The insomnia group showed higher levels of anxiety, depression, and insomnia than the healthy group, as well as increased beta
(105) = -2.56,
= 0.012 and gamma
(105) = -2.44,
= 0.016 spectra. Among all participants, insomnia symptoms positively correlated with the intensity of beta (
= 0.28,
＜ 0.01) and gamma (
= 0.25,
＜ 0.05) spectra. Through hierarchical multiple regression, the beta power showed the additional ability to predict insomnia symptoms beyond the effect of anxiety (Δ
= 0.041,
= 0.018).
: Our results showed a significant relationship between beta electroencephalographic activity and insomnia symptoms, after adjusting for other clinical correlates, and serve as further evidence for the hyperarousal theory of insomnia. Moreover, resting-state quantitative electroencephalography may be a supplementary tool to assess insomnia.
Functional immobility can cause functional disability in patients with schizophrenia and has been linked to prognosis and mortality. Although depression might be a barrier for physical activity ...engagement, scarce data are present on the relationship between depression and functional mobility (FM) in schizophrenia. Thus, we aimed to investigate the associations among FM, depression, and other clinical correlates in individuals with schizophrenia.
FM was evaluated by the pedometer-assessed daily steps and Timed Up-and-Go (TUG) test in the daily-living and clinical settings, respectively. Psychiatric symptoms were assessed using the Beck Depression Inventory, Brief Psychiatric Rating Scale (BPRS), and State-Trait Anxiety Inventory. Cognitive function was evaluated using the Sternberg Working Memory (SWM) Task. Multiple regression analyses were performed to identify predictive factors associated with FM, with adjustment for relevant covariates.
Sixty patients were enrolled in this study. Depression was the most consistent explanatory variable for both pedometer (β = -0.34, p = 0.011) and TUG time (β = 0.32, p = 0.018). Additionally, SWM accuracy (β = -0.29, p = 0.018), BPRS-Withdrawal (β = 0.19, p = 0.139), and fasting blood sugar (β = 0.34, p = 0.008) were associated with TUG time. However, psychotic symptoms and anxiety were not associated with pedometer and TUG.
We identified an association between depression and FM after adjusting for other disorder-related correlates in schizophrenia. Since the intervention goal is functional recovery, improving FM by treating depression may have considerable therapeutic value.
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